Bounded Universal Droop Control to Enable the Operation of Power Inverters Under Some Abnormal Conditions and Maintain Voltage and Frequency Within Predetermined Ranges

The universal droop control (UDC) can be applied to power inverters for achieving voltage and frequency regulation, accurate proportional power sharing, without the need of knowing the type or value of the impedance. There is an increasing need for voltage and frequency regulation within predetermined ranges even under abnormal conditions, such as overloading, sensor faults, and large set-point changes, etc. In this paper, a bounded nonlinear dynamics is introduced into the UDC to ensure that the voltage and frequency can always stay within predetermined ranges under normal and abnormal conditions, up to hardware limits when current protection needs to be triggered. As a result, the proposed controller can extend the operational range of power inverters in terms of voltage and frequency regulation to cover different scenarios. More importantly, the ranges for both voltage and frequency can be chosen independently from each other. Since the original structure of the UDC is kept in the proposed controller, the properties of the UDC, such as without the need of knowing the type or value of the impedance, are well maintained. Extensive simulation and experimental results are presented to validate the effectiveness of the proposed controller.